Securing a data segment for storage

ABSTRACT

A method begins by a dispersed storage (DS) processing module encrypting a data segment utilizing an encryption key to produce an encrypted data segment and performing a deterministic function on the encrypted data to produce a transformed representation of the encrypted data. The method continues with the DS processing module masking the encryption key utilizing the transformed representation of the encrypted data to produce a masked key, partitioning the masked key into a plurality masked key partitions, partitioning the encrypted data segment into a plurality of encrypted data segment partitions, and combining the plurality of masked key partitions with the plurality of encrypted data segment partitions to produce a plurality of combined partitions. For a combined partition of the plurality of combined partitions, the method continues with the DS processing module encoding the combined partition using a dispersed storage error coding function to produce a set of encoded data slices.

CROSS REFERENCE TO RELATED PATENTS

The present U.S. Utility patent application claims priority pursuant to35 U.S.C. §120 as a continuation of U.S. Utility application Ser. No.13/464,082, entitled “SECURING A DATA SEGMENT FOR STORAGE”, filed May 4,2012, issuing as U.S. Pat. No. 8,782,439 on Jul. 15, 2014, which claimspriority pursuant to 35 U.S.C. §119(e) to U.S. Provisional ApplicationNo. 61/493,820, entitled “DATA SECURITY IN A DISPERSED STORAGE NETWORK”,filed Jun. 6, 2011, all of which are hereby incorporated herein byreference in their entirety and made part of the present U.S. Utilitypatent application for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

NOT APPLICABLE

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

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BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

This invention relates generally to computing systems and moreparticularly to data storage solutions within such computing systems.

2. Description of Related Art

Computers are known to communicate, process, and store data. Suchcomputers range from wireless smart phones to data centers that supportmillions of web searches, stock trades, or on-line purchases every day.In general, a computing system generates data and/or manipulates datafrom one form into another. For instance, an image sensor of thecomputing system generates raw picture data and, using an imagecompression program (e.g., JPEG, MPEG, etc.), the computing systemmanipulates the raw picture data into a standardized compressed image.

With continued advances in processing speed and communication speed,computers are capable of processing real time multimedia data forapplications ranging from simple voice communications to streaming highdefinition video. As such, general-purpose information appliances arereplacing purpose-built communications devices (e.g., a telephone). Forexample, smart phones can support telephony communications but they arealso capable of text messaging and accessing the internet to performfunctions including email, web browsing, remote applications access, andmedia communications (e.g., telephony voice, image transfer, musicfiles, video files, real time video streaming. etc.).

Each type of computer is constructed and operates in accordance with oneor more communication, processing, and storage standards. As a result ofstandardization and with advances in technology, more and moreinformation content is being converted into digital formats. Forexample, more digital cameras are now being sold than film cameras, thusproducing more digital pictures. As another example, web-basedprogramming is becoming an alternative to over the air televisionbroadcasts and/or cable broadcasts. As further examples, papers, books,video entertainment, home video, etc. are now being stored digitally,which increases the demand on the storage function of computers.

A typical computer storage system includes one or more memory devicesaligned with the needs of the various operational aspects of thecomputer's processing and communication functions. Generally, theimmediacy of access dictates what type of memory device is used. Forexample, random access memory (RAM) memory can be accessed in any randomorder with a constant response time, thus it is typically used for cachememory and main memory. By contrast, memory device technologies thatrequire physical movement such as magnetic disks, tapes, and opticaldiscs, have a variable response time as the physical movement can takelonger than the data transfer, thus they are typically used forsecondary memory (e.g., hard drive, backup memory, etc.).

A computer's storage system will be compliant with one or more computerstorage standards that include, but are not limited to, network filesystem (NFS), flash file system (FFS), disk file system (DFS), smallcomputer system interface (SCSI), internet small computer systeminterface (iSCSI), file transfer protocol (FTP), and web-baseddistributed authoring and versioning (WebDAV). These standards specifythe data storage format (e.g., files, data objects, data blocks,directories, etc.) and interfacing between the computer's processingfunction and its storage system, which is a primary function of thecomputer's memory controller.

Despite the standardization of the computer and its storage system,memory devices fail; especially commercial grade memory devices thatutilize technologies incorporating physical movement (e.g., a discdrive). For example, it is fairly common for a disc drive to routinelysuffer from bit level corruption and to completely fail after threeyears of use. One solution is to a higher-grade disc drive, which addssignificant cost to a computer.

Another solution is to utilize multiple levels of redundant disc drivesto replicate the data into two or more copies. One such redundant driveapproach is called redundant array of independent discs (RAID). In aRAID device, a RAID controller adds parity data to the original databefore storing it across the array. The parity data is calculated fromthe original data such that the failure of a disc will not result in theloss of the original data. For example, RAID 5 uses three discs toprotect data from the failure of a single disc. The parity data, andassociated redundancy overhead data, reduces the storage capacity ofthree independent discs by one third (e.g., n−1=capacity). RAID 6 canrecover from a loss of two discs and requires a minimum of four discswith a storage capacity of n−2.

While RAID addresses the memory device failure issue, it is not withoutits own failures issues that affect its effectiveness, efficiency andsecurity. For instance, as more discs are added to the array, theprobability of a disc failure increases, which increases the demand formaintenance. For example, when a disc fails, it needs to be manuallyreplaced before another disc fails and the data stored in the RAIDdevice is lost. To reduce the risk of data loss, data on a RAID deviceis typically copied on to one or more other RAID devices. While thisaddresses the loss of data issue, it raises a security issue sincemultiple copies of data are available, which increases the chances ofunauthorized access. Further, as the amount of data being stored grows,the overhead of RAID devices becomes a non-trivial efficiency issue.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a computingsystem in accordance with the present invention;

FIG. 2 is a schematic block diagram of an embodiment of a computing corein accordance with the present invention;

FIG. 3 is a schematic block diagram of an embodiment of a distributedstorage processing unit in accordance with the present invention;

FIG. 4 is a schematic block diagram of an embodiment of a grid module inaccordance with the present invention;

FIG. 5 is a diagram of an example embodiment of error coded data slicecreation in accordance with the present invention;

FIG. 6A is a schematic block diagram of another embodiment of acomputing system in accordance with the present invention;

FIG. 6B is a table illustrating an example of a dispersed storage (DS)unit key pair to DS unit key assignment table in accordance with thepresent invention;

FIG. 7A is a schematic block diagram of another embodiment of acomputing system in accordance with the present invention;

FIG. 7B is a flowchart illustrating an example of rebuilding a slice inaccordance with the present invention;

FIG. 8 is a flowchart illustrating another example of generating anencrypted partial slice in accordance with the present invention;

FIG. 9A is a schematic block diagram of another embodiment of acomputing system in accordance with the present invention;

FIG. 9B is a schematic block diagram of another embodiment of acomputing system in accordance with the present invention;

FIG. 9C is a flowchart illustrating an example of updating software inaccordance with the present invention;

FIG. 10A is a flowchart illustrating an example of encrypting an encodeddata slice in accordance with the present invention;

FIG. 10B is a flowchart illustrating an example of decrypting anencrypted data slice in accordance with the present invention;

FIG. 11A is a flowchart illustrating an example of storing a datasegment in accordance with the present invention;

FIG. 11B is a flowchart illustrating an example of retrieving a datasegment in accordance with the present invention;

FIG. 12A is a schematic block diagram of another embodiment of acomputing system in accordance with the present invention;

FIG. 12B is a flowchart illustrating an example of securing a datasegment in accordance with the present invention;

FIG. 13A is a schematic block diagram of another embodiment of dispersedstorage processing module in accordance with the present invention;

FIG. 13B is a flowchart illustrating another example of retrieving adata segment in accordance with the present invention;

FIG. 14 is a diagram illustrating an example of a segmentationallocation table (SAT) in accordance with the present invention;

FIG. 15A is a diagram illustrating an example of a slice name format inaccordance with the present invention;

FIG. 15B is a diagram illustrating an example of data segmentation inaccordance with the present invention;

FIG. 15C is a diagram illustrating another example of data segmentationin accordance with the present invention;

FIG. 16A is a schematic block diagram of another embodiment of acomputing system in accordance with the present invention; and

FIG. 16B is a flowchart illustrating an example of storing segmenteddata in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of a computing system 10 thatincludes one or more of a first type of user devices 12, one or more ofa second type of user devices 14, at least one distributed storage (DS)processing unit 16, at least one DS managing unit 18, at least onestorage integrity processing unit 20, and a distributed storage network(DSN) memory 22 coupled via a network 24. The network 24 may include oneor more wireless and/or wire lined communication systems; one or moreprivate intranet systems and/or public internet systems; and/or one ormore local area networks (LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of distributed storage (DS) units36 for storing data of the system. Each of the DS units 36 includes aprocessing module and memory and may be located at a geographicallydifferent site than the other DS units (e.g., one in Chicago, one inMilwaukee, etc.).

Each of the user devices 12-14, the DS processing unit 16, the DSmanaging unit 18, and the storage integrity processing unit 20 may be aportable computing device (e.g., a social networking device, a gamingdevice, a cell phone, a smart phone, a personal digital assistant, adigital music player, a digital video player, a laptop computer, ahandheld computer, a video game controller, and/or any other portabledevice that includes a computing core) and/or a fixed computing device(e.g., a personal computer, a computer server, a cable set-top box, asatellite receiver, a television set, a printer, a fax machine, homeentertainment equipment, a video game console, and/or any type of homeor office computing equipment). Such a portable or fixed computingdevice includes a computing core 26 and one or more interfaces 30, 32,and/or 33. An embodiment of the computing core 26 will be described withreference to FIG. 2.

With respect to the interfaces, each of the interfaces 30, 32, and 33includes software and/or hardware to support one or more communicationlinks via the network 24 indirectly and/or directly. For example,interfaces 30 support a communication link (wired, wireless, direct, viaa LAN, via the network 24, etc.) between the first type of user device14 and the DS processing unit 16. As another example, DSN interface 32supports a plurality of communication links via the network 24 betweenthe DSN memory 22 and the DS processing unit 16, the first type of userdevice 12, and/or the storage integrity processing unit 20. As yetanother example, interface 33 supports a communication link between theDS managing unit 18 and any one of the other devices and/or units 12,14, 16, 20, and/or 22 via the network 24.

In general and with respect to data storage, the system 10 supportsthree primary functions: distributed network data storage management,distributed data storage and retrieval, and data storage integrityverification. In accordance with these three primary functions, data canbe distributedly stored in a plurality of physically different locationsand subsequently retrieved in a reliable and secure manner regardless offailures of individual storage devices, failures of network equipment,the duration of storage, the amount of data being stored, attempts athacking the data, etc.

The DS managing unit 18 performs distributed network data storagemanagement functions, which include establishing distributed datastorage parameters, performing network operations, performing networkadministration, and/or performing network maintenance. The DS managingunit 18 establishes the distributed data storage parameters (e.g.,allocation of virtual DSN memory space, distributed storage parameters,security parameters, billing information, user profile information,etc.) for one or more of the user devices 12-14 (e.g., established forindividual devices, established for a user group of devices, establishedfor public access by the user devices, etc.). For example, the DSmanaging unit 18 coordinates the creation of a vault (e.g., a virtualmemory block) within the DSN memory 22 for a user device (for a group ofdevices, or for public access). The DS managing unit 18 also determinesthe distributed data storage parameters for the vault. In particular,the DS managing unit 18 determines a number of slices (e.g., the numberthat a data segment of a data file and/or data block is partitioned intofor distributed storage) and a read threshold value (e.g., the minimumnumber of slices required to reconstruct the data segment).

As another example, the DS managing module 18 creates and stores,locally or within the DSN memory 22, user profile information. The userprofile information includes one or more of authentication information,permissions, and/or the security parameters. The security parameters mayinclude one or more of encryption/decryption scheme, one or moreencryption keys, key generation scheme, and data encoding/decodingscheme.

As yet another example, the DS managing unit 18 creates billinginformation for a particular user, user group, vault access, publicvault access, etc. For instance, the DS managing unit 18 tracks thenumber of times user accesses a private vault and/or public vaults,which can be used to generate a per-access bill. In another instance,the DS managing unit 18 tracks the amount of data stored and/orretrieved by a user device and/or a user group, which can be used togenerate a per-data-amount bill.

The DS managing unit 18 also performs network operations, networkadministration, and/or network maintenance. As at least part ofperforming the network operations and/or administration, the DS managingunit 18 monitors performance of the devices and/or units of the system10 for potential failures, determines the devices and/or unit'sactivation status, determines the devices' and/or units' loading, andany other system level operation that affects the performance level ofthe system 10. For example, the DS managing unit 18 receives andaggregates network management alarms, alerts, errors, statusinformation, performance information, and messages from the devices12-14 and/or the units 16, 20, 22. For example, the DS managing unit 18receives a simple network management protocol (SNMP) message regardingthe status of the DS processing unit 16.

The DS managing unit 18 performs the network maintenance by identifyingequipment within the system 10 that needs replacing, upgrading,repairing, and/or expanding. For example, the DS managing unit 18determines that the DSN memory 22 needs more DS units 36 or that one ormore of the DS units 36 needs updating.

The second primary function (i.e., distributed data storage andretrieval) begins and ends with a user device 12-14. For instance, if asecond type of user device 14 has a data file 38 and/or data block 40 tostore in the DSN memory 22, it send the data file 38 and/or data block40 to the DS processing unit 16 via its interface 30. As will bedescribed in greater detail with reference to FIG. 2, the interface 30functions to mimic a conventional operating system (OS) file systeminterface (e.g., network file system (NFS), flash file system (FFS),disk file system (DFS), file transfer protocol (FTP), web-baseddistributed authoring and versioning (WebDAV), etc.) and/or a blockmemory interface (e.g., small computer system interface (SCSI), internetsmall computer system interface (iSCSI), etc.). In addition, theinterface 30 may attach a user identification code (ID) to the data file38 and/or data block 40.

The DS processing unit 16 receives the data file 38 and/or data block 40via its interface 30 and performs a distributed storage (DS) process 34thereon (e.g., an error coding dispersal storage function). The DSprocessing 34 begins by partitioning the data file 38 and/or data block40 into one or more data segments, which is represented as Y datasegments. For example, the DS processing 34 may partition the data file38 and/or data block 40 into a fixed byte size segment (e.g., 2¹ to2^(n) bytes, where n=>2) or a variable byte size (e.g., change byte sizefrom segment to segment, or from groups of segments to groups ofsegments, etc.).

For each of the Y data segments, the DS processing 34 error encodes(e.g., forward error correction (FEC), information dispersal algorithm,or error correction coding) and slices (or slices then error encodes)the data segment into a plurality of error coded (EC) data slices 42-48,which is represented as X slices per data segment. The number of slices(X) per segment, which corresponds to a number of pillars n, is set inaccordance with the distributed data storage parameters and the errorcoding scheme. For example, if a Reed-Solomon (or other FEC scheme) isused in an n/k system, then a data segment is divided into n slices,where k number of slices is needed to reconstruct the original data(i.e., k is the threshold). As a few specific examples, the n/k factormay be 5/3; 6/4; 8/6; 8/5; 16/10.

For each slice 42-48, the DS processing unit 16 creates a unique slicename and appends it to the corresponding slice 42-48. The slice nameincludes universal DSN memory addressing routing information (e.g.,virtual memory addresses in the DSN memory 22) and user-specificinformation (e.g., user ID, file name, data block identifier, etc.).

The DS processing unit 16 transmits the plurality of EC slices 42-48 toa plurality of DS units 36 of the DSN memory 22 via the DSN interface 32and the network 24. The DSN interface 32 formats each of the slices fortransmission via the network 24. For example, the DSN interface 32 mayutilize an internet protocol (e.g., TCP/IP, etc.) to packetize theslices 42-48 for transmission via the network 24.

The number of DS units 36 receiving the slices 42-48 is dependent on thedistributed data storage parameters established by the DS managing unit18. For example, the DS managing unit 18 may indicate that each slice isto be stored in a different DS unit 36. As another example, the DSmanaging unit 18 may indicate that like slice numbers of different datasegments are to be stored in the same DS unit 36. For example, the firstslice of each of the data segments is to be stored in a first DS unit36, the second slice of each of the data segments is to be stored in asecond DS unit 36, etc. In this manner, the data is encoded anddistributedly stored at physically diverse locations to improved datastorage integrity and security.

Each DS unit 36 that receives a slice 42-48 for storage translates thevirtual DSN memory address of the slice into a local physical addressfor storage. Accordingly, each DS unit 36 maintains a virtual tophysical memory mapping to assist in the storage and retrieval of data.

The first type of user device 12 performs a similar function to storedata in the DSN memory 22 with the exception that it includes the DSprocessing. As such, the device 12 encodes and slices the data fileand/or data block it has to store. The device then transmits the slices11 to the DSN memory via its DSN interface 32 and the network 24.

For a second type of user device 14 to retrieve a data file or datablock from memory, it issues a read command via its interface 30 to theDS processing unit 16. The DS processing unit 16 performs the DSprocessing 34 to identify the DS units 36 storing the slices of the datafile and/or data block based on the read command. The DS processing unit16 may also communicate with the DS managing unit 18 to verify that theuser device 14 is authorized to access the requested data.

Assuming that the user device is authorized to access the requesteddata, the DS processing unit 16 issues slice read commands to at least athreshold number of the DS units 36 storing the requested data (e.g., toat least 10 DS units for a 16/10 error coding scheme). Each of the DSunits 36 receiving the slice read command, verifies the command,accesses its virtual to physical memory mapping, retrieves the requestedslice, or slices, and transmits it to the DS processing unit 16.

Once the DS processing unit 16 has received a read threshold number ofslices for a data segment, it performs an error decoding function andde-slicing to reconstruct the data segment. When Y number of datasegments has been reconstructed, the DS processing unit 16 provides thedata file 38 and/or data block 40 to the user device 14. Note that thefirst type of user device 12 performs a similar process to retrieve adata file and/or data block.

The storage integrity processing unit 20 performs the third primaryfunction of data storage integrity verification. In general, the storageintegrity processing unit 20 periodically retrieves slices 45, and/orslice names, of a data file or data block of a user device to verifythat one or more slices have not been corrupted or lost (e.g., the DSunit failed). The retrieval process mimics the read process previouslydescribed.

If the storage integrity processing unit 20 determines that one or moreslices is corrupted or lost, it rebuilds the corrupted or lost slice(s)in accordance with the error coding scheme. The storage integrityprocessing unit 20 stores the rebuild slice, or slices, in theappropriate DS unit(s) 36 in a manner that mimics the write processpreviously described.

FIG. 2 is a schematic block diagram of an embodiment of a computing core26 that includes a processing module 50, a memory controller 52, mainmemory 54, a video graphics processing unit 55, an input/output (IO)controller 56, a peripheral component interconnect (PCI) interface 58,at least one IO device interface module 62, a read only memory (ROM)basic input output system (BIOS) 64, and one or more memory interfacemodules. The memory interface module(s) includes one or more of auniversal serial bus (USB) interface module 66, a host bus adapter (HBA)interface module 68, a network interface module 70, a flash interfacemodule 72, a hard drive interface module 74, and a DSN interface module76. Note the DSN interface module 76 and/or the network interface module70 may function as the interface 30 of the user device 14 of FIG. 1.Further note that the IO device interface module 62 and/or the memoryinterface modules may be collectively or individually referred to as IOports.

FIG. 3 is a schematic block diagram of an embodiment of a dispersedstorage (DS) processing module 34 of user device 12 and/or of the DSprocessing unit 16. The DS processing module 34 includes a gatewaymodule 78, an access module 80, a grid module 82, and a storage module84. The DS processing module 34 may also include an interface 30 and theDSnet interface 32 or the interfaces 68 and/or 70 may be part of user 12or of the DS processing unit 14. The DS processing module 34 may furtherinclude a bypass/feedback path between the storage module 84 to thegateway module 78. Note that the modules 78-84 of the DS processingmodule 34 may be in a single unit or distributed across multiple units.

In an example of storing data, the gateway module 78 receives anincoming data object that includes a user ID field 86, an object namefield 88, and the data field 40 and may also receive correspondinginformation that includes a process identifier (e.g., an internalprocess/application ID), metadata, a file system directory, a blocknumber, a transaction message, a user device identity (ID), a dataobject identifier, a source name, and/or user information. The gatewaymodule 78 authenticates the user associated with the data object byverifying the user ID 86 with the managing unit 18 and/or anotherauthenticating unit.

When the user is authenticated, the gateway module 78 obtains userinformation from the management unit 18, the user device, and/or theother authenticating unit. The user information includes a vaultidentifier, operational parameters, and user attributes (e.g., userdata, billing information, etc.). A vault identifier identifies a vault,which is a virtual memory space that maps to a set of DS storage units36. For example, vault 1 (i.e., user 1's DSN memory space) includeseight DS storage units (X=8 wide) and vault 2 (i.e., user 2's DSN memoryspace) includes sixteen DS storage units (X=16 wide). The operationalparameters may include an error coding algorithm, the width n (number ofpillars X or slices per segment for this vault), a read threshold T, awrite threshold, an encryption algorithm, a slicing parameter, acompression algorithm, an integrity check method, caching settings,parallelism settings, and/or other parameters that may be used to accessthe DSN memory layer.

The gateway module 78 uses the user information to assign a source name35 to the data. For instance, the gateway module 60 determines thesource name 35 of the data object 40 based on the vault identifier andthe data object. For example, the source name may contain a fileidentifier (ID), a vault generation number, a reserved field, and avault identifier (ID). As another example, the gateway module 78 maygenerate the file ID based on a hash function of the data object 40.Note that the gateway module 78 may also perform message conversion,protocol conversion, electrical conversion, optical conversion, accesscontrol, user identification, user information retrieval, trafficmonitoring, statistics generation, configuration, management, and/orsource name determination.

The access module 80 receives the data object 40 and creates a series ofdata segments 1 through Y 90-92 in accordance with a data storageprotocol (e.g., file storage system, a block storage system, and/or anaggregated block storage system). The number of segments Y may be chosenor randomly assigned based on a selected segment size and the size ofthe data object. For example, if the number of segments is chosen to bea fixed number, then the size of the segments varies as a function ofthe size of the data object. For instance, if the data object is animage file of 4,194,304 eight bit bytes (e.g., 33,554,432 bits) and thenumber of segments Y=131,072, then each segment is 256 bits or 32 bytes.As another example, if segment sized is fixed, then the number ofsegments Y varies based on the size of data object. For instance, if thedata object is an image file of 4,194,304 bytes and the fixed size ofeach segment is 4,096 bytes, the then number of segments Y=1,024. Notethat each segment is associated with the same source name.

The grid module 82 receives the data segments and may manipulate (e.g.,compression, encryption, cyclic redundancy check (CRC), etc.) each ofthe data segments before performing an error coding function of theerror coding dispersal storage function to produce a pre-manipulateddata segment. After manipulating a data segment, if applicable, the gridmodule 82 error encodes (e.g., Reed-Solomon, Convolution encoding,Trellis encoding, etc.) the data segment or manipulated data segmentinto X error coded data slices 42-44.

The value X, or the number of pillars (e.g., X=16), is chosen as aparameter of the error coding dispersal storage function. Otherparameters of the error coding dispersal function include a readthreshold T, a write threshold W, etc. The read threshold (e.g., T=10,when X=16) corresponds to the minimum number of error-free error codeddata slices required to reconstruct the data segment. In other words,the DS processing module 34 can compensate for X−T (e.g., 16−10=6)missing error coded data slices per data segment. The write threshold Wcorresponds to a minimum number of DS storage units that acknowledgeproper storage of their respective data slices before the DS processingmodule indicates proper storage of the encoded data segment. Note thatthe write threshold is greater than or equal to the read threshold for agiven number of pillars (X).

For each data slice of a data segment, the grid module 82 generates aunique slice name 37 and attaches it thereto. The slice name 37 includesa universal routing information field and a vault specific field and maybe 48 bytes (e.g., 24 bytes for each of the universal routinginformation field and the vault specific field). As illustrated, theuniversal routing information field includes a slice index, a vault ID,a vault generation, and a reserved field. The slice index is based onthe pillar number and the vault ID and, as such, is unique for eachpillar (e.g., slices of the same pillar for the same vault for anysegment will share the same slice index). The vault specific fieldincludes a data name, which includes a file ID and a segment number(e.g., a sequential numbering of data segments 1-Y of a simple dataobject or a data block number).

Prior to outputting the error coded data slices of a data segment, thegrid module may perform post-slice manipulation on the slices. Ifenabled, the manipulation includes slice level compression, encryption,CRC, addressing, tagging, and/or other manipulation to improve theeffectiveness of the computing system.

When the error coded data slices of a data segment are ready to beoutputted, the grid module 82 determines which of the DS storage units36 will store the EC data slices based on a dispersed storage memorymapping associated with the user's vault and/or DS storage unitattributes. The DS storage unit attributes may include availability,self-selection, performance history, link speed, link latency,ownership, available DSN memory, domain, cost, a prioritization scheme,a centralized selection message from another source, a lookup table,data ownership, and/or any other factor to optimize the operation of thecomputing system. Note that the number of DS storage units 36 is equalto or greater than the number of pillars (e.g., X) so that no more thanone error coded data slice of the same data segment is stored on thesame DS storage unit 36. Further note that EC data slices of the samepillar number but of different segments (e.g., EC data slice 1 of datasegment 1 and EC data slice 1 of data segment 2) may be stored on thesame or different DS storage units 36.

The storage module 84 performs an integrity check on the outboundencoded data slices and, when successful, identifies a plurality of DSstorage units based on information provided by the grid module 82. Thestorage module 84 then outputs the encoded data slices 1 through X ofeach segment 1 through Y to the DS storage units 36. Each of the DSstorage units 36 stores its EC data slice(s) and maintains a localvirtual DSN address to physical location table to convert the virtualDSN address of the EC data slice(s) into physical storage addresses.

In an example of a read operation, the user device 12 and/or 14 sends aread request to the DS processing unit 14, which authenticates therequest. When the request is authentic, the DS processing unit 14 sendsa read message to each of the DS storage units 36 storing slices of thedata object being read. The slices are received via the DSnet interface32 and processed by the storage module 84, which performs a parity checkand provides the slices to the grid module 82 when the parity check wassuccessful. The grid module 82 decodes the slices in accordance with theerror coding dispersal storage function to reconstruct the data segment.The access module 80 reconstructs the data object from the data segmentsand the gateway module 78 formats the data object for transmission tothe user device.

FIG. 4 is a schematic block diagram of an embodiment of a grid module 82that includes a control unit 73, a pre-slice manipulator 75, an encoder77, a slicer 79, a post-slice manipulator 81, a pre-slice de-manipulator83, a decoder 85, a de-slicer 87, and/or a post-slice de-manipulator 89.Note that the control unit 73 may be partially or completely external tothe grid module 82. For example, the control unit 73 may be part of thecomputing core at a remote location, part of a user device, part of theDS managing unit 18, or distributed amongst one or more DS storageunits.

In an example of write operation, the pre-slice manipulator 75 receivesa data segment 90-92 and a write instruction from an authorized userdevice. The pre-slice manipulator 75 determines if pre-manipulation ofthe data segment 90-92 is required and, if so, what type. The pre-slicemanipulator 75 may make the determination independently or based oninstructions from the control unit 73, where the determination is basedon a computing system-wide predetermination, a table lookup, vaultparameters associated with the user identification, the type of data,security requirements, available DSN memory, performance requirements,and/or other metadata.

Once a positive determination is made, the pre-slice manipulator 75manipulates the data segment 90-92 in accordance with the type ofmanipulation. For example, the type of manipulation may be compression(e.g., Lempel-Ziv-Welch, Huffman, Golomb, fractal, wavelet, etc.),signatures (e.g., Digital Signature Algorithm (DSA), Elliptic Curve DSA,Secure Hash Algorithm, etc.), watermarking, tagging, encryption (e.g.,Data Encryption Standard, Advanced Encryption Standard, etc.), addingmetadata (e.g., time/date stamping, user information, file type, etc.),cyclic redundancy check (e.g., CRC32), and/or other data manipulationsto produce the pre-manipulated data segment.

The encoder 77 encodes the pre-manipulated data segment 92 using aforward error correction (FEC) encoder (and/or other type of erasurecoding and/or error coding) to produce an encoded data segment 94. Theencoder 77 determines which forward error correction algorithm to usebased on a predetermination associated with the user's vault, a timebased algorithm, user direction, DS managing unit direction, controlunit direction, as a function of the data type, as a function of thedata segment 92 metadata, and/or any other factor to determine algorithmtype. The forward error correction algorithm may be Golay,Multidimensional parity, Reed-Solomon, Hamming, Bose Ray ChauduriHocquenghem (BCH), Cauchy-Reed-Solomon, or any other FEC encoder. Notethat the encoder 77 may use a different encoding algorithm for each datasegment 92, the same encoding algorithm for the data segments 92 of adata object, or a combination thereof.

The encoded data segment 94 is of greater size than the data segment 92by the overhead rate of the encoding algorithm by a factor of X/T, whereX is the width or number of slices, and T is the read threshold. In thisregard, the corresponding decoding process can accommodate at most X−Tmissing EC data slices and still recreate the data segment 92. Forexample, if X=16 and T=10, then the data segment 92 will be recoverableas long as 10 or more EC data slices per segment are not corrupted.

The slicer 79 transforms the encoded data segment 94 into EC data slicesin accordance with the slicing parameter from the vault for this userand/or data segment 92. For example, if the slicing parameter is X=16,then the slicer 79 slices each encoded data segment 94 into 16 encodedslices.

The post-slice manipulator 81 performs, if enabled, post-manipulation onthe encoded slices to produce the EC data slices. If enabled, thepost-slice manipulator 81 determines the type of post-manipulation,which may be based on a computing system-wide predetermination,parameters in the vault for this user, a table lookup, the useridentification, the type of data, security requirements, available DSNmemory, performance requirements, control unit directed, and/or othermetadata. Note that the type of post-slice manipulation may includeslice level compression, signatures, encryption, CRC, addressing,watermarking, tagging, adding metadata, and/or other manipulation toimprove the effectiveness of the computing system.

In an example of a read operation, the post-slice de-manipulator 89receives at least a read threshold number of EC data slices and performsthe inverse function of the post-slice manipulator 81 to produce aplurality of encoded slices. The de-slicer 87 de-slices the encodedslices to produce an encoded data segment 94. The decoder 85 performsthe inverse function of the encoder 77 to recapture the data segment90-92. The pre-slice de-manipulator 83 performs the inverse function ofthe pre-slice manipulator 75 to recapture the data segment 90-92.

FIG. 5 is a diagram of an example of slicing an encoded data segment 94by the slicer 79. In this example, the encoded data segment 94 includesthirty-two bits, but may include more or less bits. The slicer 79disperses the bits of the encoded data segment 94 across the EC dataslices in a pattern as shown. As such, each EC data slice does notinclude consecutive bits of the data segment 94 reducing the impact ofconsecutive bit failures on data recovery. For example, if EC data slice2 (which includes bits 1, 5, 9, 13, 17, 25, and 29) is unavailable(e.g., lost, inaccessible, or corrupted), the data segment can bereconstructed from the other EC data slices (e.g., 1, 3 and 4 for a readthreshold of 3 and a width of 4).

FIG. 6A is a schematic block diagram of another embodiment of acomputing system. The system includes a plurality of sites 1-4 thatincludes, in totality, a set of dispersed storage (DS) units associatedwith a set of encoded data slices. The set of encoded data slices isproduced by dispersed storage error encoding a data segment. Each suchsite of the plurality of sites 1-4 includes at least one DS unit of theset of DS units, wherein the at least one DS unit stores a correspondingencoded data slice of the set of encoded data slices. For example, site1 includes DS units 1-2, site 2 includes DS units 3-4, site 3 includesDS units 5-6, and site 4 includes DS units 7-8 when a pillar width is 8.

Rebuilding an encoded data slice requires at least a decode thresholdnumber of encoded data slices of a set of encoded data slices associatedwith the encoded data slice to be rebuilt. For example, DS unit 2requests a decode threshold number of encoded data slices from DS units1, 3, 4, 5, and 6 when DS unit 2 is associated with an encoded dataslice to be rebuilt and the decode threshold number is 5. Each DS unitof DS units 1, 3, 4, 5, and 6 sends a corresponding encoded data slice(e.g., DS unit 4 sends a pillar 4 encoded data slice) to DS unit 2. DSunit 2 receives the decode threshold number of encoded data slices anddispersed storage error decodes the decode threshold number of encodeddata slices to reproduce a data segment. DS unit 2 dispersed storageerror encodes the data segment to produce the set of encoded dataslices. DS unit 2 selects the encoded data slice associated with DS unit2 (e.g., pillar 2) as a copy of the encoded data slice to be rebuilt andstores the encoded data slice to be rebuilt.

Alternatively, DS unit 2 requests a decode threshold number of slicepartials from DS units 1, 3, 4, 5, and 6 when DS unit 2 is associatedwith the encoded data slice to be rebuilt and the decode thresholdnumber is 5. Each DS unit of DS units 1, 3, 4, 5, and 6 generates aslice partial (e.g., DS unit 4 generates a pillar 4 slice partial) basedon rebuilding parameters and an encoded data slice associated with theDS unit. The rebuilding parameters includes one or more of the dispersedstorage error coding parameters, such as a pillar width (e.g., 8), adecode threshold (e.g., 5), a pillar index to be rebuilt (e.g., pillar2), the rebuilding participant list (e.g., DS units 1, 3, 4, 5, and 6),a rebuilding topology (e.g., DS unit 1 to DS unit 2, DS unit 3 to DSunit 4 to DS unit 2, DS unit 5 to DS unit 6 to DS unit 2), an encodingmatrix, a DS unit pair key indicator, a DS unit key assignment, DiffieHellman parameters, and an encryption algorithm indicator. For example,DS unit 4 generates partial (2,4)=(inverted square matrix of an encodingmatrix utilizing participating rows 1, 3, 4, 5, 6)*(a data matrix with apillar 4 encoded data slice in a third row)*(a second row of theencoding matrix corresponding to a pillar number of the encoded dataslice to be rebuilt).

Next, each DS unit of DS units 1, 3, 4, 5, and 6 encrypts the slicepartial corresponding to the DS unit utilizing an encryption function,wherein the encryption function utilizes an encryption algorithm and oneor more keys. The encryption algorithm includes performing an exclusiveor (XOR) logical function on the slice partial and the one or more keys.Each key of the one or more keys may be utilized an even number of timesby the DS unit and at least one other DS unit of DS units 1, 3, 4, 5,and 6 to enable subsequent decryption (e.g., XOR) when the decodethreshold number of slice partials are combined to reproduce the encodeddata slice to be rebuilt. For instance, each DS unit may utilize eachpossible key enabled for use by the DS unit. Each key of the one or morekeys may be obtained by one or more of a retrieval request, a message,and generation. For example, DS unit 3 utilizes a shared secret key(K3-5) shared between DS units 3 and 5, DS unit 5 utilizes the sharedsecret key between DS units 3 and 5, DS unit 4 utilizes a shared secretkey (K1-4) between DS units 1 and 4, DS unit 6 utilizes a shared secretkey (K1-6) between DS units 1 and 6, and DS unit 1 utilizes the sharedsecret key between DS units 1 and 4 the shared secret key between DSunits 1 and 6 in accordance with DS unit pair key indicators and a DSunit key assignment of the rebuilding parameters.

Each DS unit may generate one or more keys associated with one or moreDS unit pairings utilizing a Diffie Hellman method and Diffie Hellmanparameters of the rebuilding parameters. As an instance of encrypting aslice partial corresponding to DS unit 3, DS unit 3 produces anencrypted slice partial in accordance with a formula: (K3-5)⊕partial(2,3). As an instance of encrypting a slice partial corresponding to DSunit 1, DS unit 1 produces an encrypted slice partial in accordance witha formula: (K1-4)⊕(K1-6)⊕partial (2,1). As an instance of encrypting aslice partial corresponding to DS unit 4, DS unit 4 produces anencrypted slice partial in accordance with a formula: (K1-4)⊕partial(2,4).

Next, each DS unit outputs an encrypted slice partial in accordance witha rebuilding topology of the rebuilding parameters. For example, DS unit1 sends the encrypted slice partial associated with DS unit 1 directlyto DS unit 2 and DS unit 3 sends the encrypted slice partial associatedwith DS unit 3 to DS unit 4 (e.g., at the same site) in accordance withthe rebuilding topology. DS unit 4 receives the encrypted slice partialassociated with DS unit 3 and combines the encrypted slice partialassociated with DS unit 3 with the encrypted slice partial associatedwith DS unit 4 in accordance with the rebuilding topology. For instance,DS unit 4 combines the encrypted slice partial associated with DS unit 3with the encrypted slice partial associated with DS unit 4 utilizing aXOR function in accordance with the formula: combined encrypted slicepartial=(K3-5)⊕partial (2,3)⊕(K1-4)⊕partial (2,4). DS unit 4 sends thecombined encrypted slice partial to DS unit 2 in accordance with therebuilding topology.

Next, DS unit 2 receives the decode threshold number of encrypted slicepartials as one or more encrypted slice partials and/or one or morecombined encrypted slice partials. DS unit 2 combines the one or moreencrypted slice partials and/or the one or more combined encrypted slicepartials utilizing a decryption algorithm (e.g., XOR) to reproduce theencoded data slice to be rebuilt. For instance, DS unit 2 reproduces theencoded data slice to be rebuilt utilizing a decryption algorithm inaccordance with a formula: rebuilt encoded data slice2=(K1-4)⊕(K1-6)⊕partial(2,1)⊕(K3-5)⊕partial(2,3) ⊕(K1-4)⊕partial(2,4)⊕(K3-5)⊕partial (2,5)⊕(K1-6)⊕partial (2,6). The decryptionalgorithm cancels the even number utilization of each key to produce anXOR sequence of the slice partials. The XOR of the slice partialsreproduces the encoded data slice to be rebuilt. In such an alternative,information leakage is minimized as encoded data slices are not exposedand slice partials are encrypted.

FIG. 6B is a table illustrating an example of a dispersed storage (DS)unit key pair to DS unit key assignment table. The table includes a DSunit pair key field 102, and a DS unit key assignment field 104. The DSunit pair key field 102 includes a plurality of DS unit pair keysentries, wherein each key entry of the plurality of DS unit pair keyentries includes two DS unit identifiers (IDs) of a corresponding DSunit pair enabled to utilize the key entry. For example, an entryincluding K1-3 corresponds to a DS unit pair key to be utilized only byDS units 1 and 3. For instance, key K1-3 is generated by DS units 1 and3 utilizing a Diffie Hellman approach. A number of entries of the DSunit pair key field may be based on a security requirement, a number ofDS units, a rebuilding topology, and a network topology.

The DS unit key assignment field 104 includes two or more DS unitidentifier (ID) fields corresponding to two or more DS units included ina DS unit storage set providing key assignments. An entry (e.g., “X”)associated with a DS unit signifies that the DS unit is assigned toutilize a corresponding DS unit pair key of a corresponding row of thetable. For example, two X entries in a column corresponding to DS unit 1signifies that DS unit 1 is to utilize keys K1-4 and key K1-6.

The key assignments may be assigned in a variety of ways based on therebuilding topology and assignment goals, wherein such assignment goalsinclude one or more of a security goal, a performance goal, and aprocessing loading goal. For example, assigned keys should not include akey that is shared between a DS unit pair when a first DS unit of the DSunit pair sends an encrypted slice partial to a second DS unit of the DSunit pair to avoid information leakage that may occur when the second DSunit combines the encrypted slice partials. As another example, eachassigned key should be utilized an even number of times such that eachassigned key cancels out (e.g., via an XOR function) when a requestingentity decodes encrypted slice partials to reproduce an encoded dataslice to be rebuilt. A method to determine and utilize keys is discussedin greater detail with reference to FIGS. 7A-8.

FIG. 7A is a schematic block diagram of another embodiment of acomputing system that includes a requesting entity 105, a computingdevice 106, and a plurality of dispersed storage (DS) units 36. Therequesting entity 105 may be implemented as at least one of a DSprocessing unit, a user device, another DS unit 36, a storage integrityprocessing unit, and a DS managing unit 18 of a distributed storagenetwork (DSN). For example, the requesting entity 105 includes the otherDS unit 36 that is rebuilding an encoded data slice. The computingdevice 106 may be implemented as at least one of a DS unit 36 and a userdevice. For example, the computing device 106 is a DS unit 36 of adecode threshold number of DS units 36 that includes at least some ofthe plurality of DS units 36, wherein the decode threshold number of DSunits 36 assist the requesting entity 105 to rebuild the encoded dataslice. The computing device 106 includes a DS module 111 and a memory112. The memory 112 may be implemented utilizing one or more memorydevices including one or more of a FLASH memory, random access memory, amagnetic disk drive, and an optical disk drive. The computing device 106may utilize the memory 112 when the computing device is the DS unit 36to facilitate storing of one or more encoded data slices. The DS module111 includes a receive request module 113, a generate partial slicemodule 114, and a encrypt partial slice module 115.

The receive request module 113, when operable within the computingdevice 106, receives a rebuild request 116 regarding an encoded dataslice. For example, the receive request module 113 receives the rebuildrequest 116 from the requesting entity 105 when the requesting entity105 facilitates rebuilding of the encoded data slice by issuing arebuild request regarding the encoded data slice to at least some of aset of DS units 36 of the plurality of DS units 36. The rebuild requestincludes one or more of rebuilding participant identifiers (IDs), DiffieHellman parameters, a rebuilding topology, a number of keys to utilizeindicator, a DS unit pair key indicator, a DS unit key assignment, apillar index to rebuild indicator, a slice name list, a requestingentity identifier (ID), a key generation algorithm, a key generationalgorithm ID, and rebuilding parameters. The rebuilding parametersincludes one or more of a pillar width, a decode threshold number, apillar index to be rebuilt, a rebuilding participant list (e.g., DSunits IDs), a rebuilding topology (e.g., DS unit 1 to DS unit 2, DS unit3 to DS unit 4 to DS unit 2, DS unit 5 to DS unit 6 to DS unit 2), anencoding matrix, a square matrix, and an inverted square matrix.

The generate partial slice module 114, when operable within thecomputing device, generates a partial slice 117 corresponding to theencoded data slice to be rebuilt based on an encoded data slice 118 thatincludes one of a set of encoded data slices stored by the computingdevice 106 (e.g., a DS unit 36) that includes the DS module 111. Forexample, the generate partial slice module 114 identifies the encodeddata slice 118 based on the rebuild request 116, retrieves the encodeddata slice 118 from memory 112, and generates the partial slice 117utilizing the encoded data slice 118 based on the rebuild request 116(e.g., based on rebuilding parameters). The generating the partial slice117 includes one or more of obtaining an encoding matrix utilized togenerate the encoded data slice (e.g., extract from the rebuild request116, retrieve from memory 112), reducing the encoding matrix to producea square matrix that exclusively includes rows identified in the partialrebuilding request (e.g., slice pillars associated with participating DSunits of a decode threshold number of DS units), inverting the squarematrix to produce an inverted matrix (e.g., alternatively, may extractthe inverted matrix from the rebuild request 116), matrix multiplyingthe inverted matrix by the encoded data slice 118 to produce a vector,and matrix multiplying the vector by a row of the encoding matrixcorresponding to the encoded data slice to be rebuilt (e.g.,alternatively, may extract the row from the rebuild request 116) toproduce the partial slice 117. For example, when a pillar 2 encoded dataslice is to be rebuilt, a DS unit 4 generates partial slice(2,4)=(inverted square matrix of an encoding matrix utilizingparticipating rows 1, 3, 4, 5, 6)*(a data matrix with a pillar 4 encodeddata slice in a third row)*(a second row of the encoding matrixcorresponding to a pillar number of the encoded data slice to berebuilt) when a decode threshold is 5 and a pillar width is 8.

The encrypt partial slice module 115, when operable within the computingdevice 106, encrypts the partial slice 117 using an encryption key of aset of encryption keys to produce an encrypted partial slice 119,wherein the encryption key is used by another DS module 111 of anotherDS unit 36 to produce another encrypted partial slice 119. The encryptpartial slice module 115 is further operable to generate, in conjunctionwith the other DS module 111, a shared secret and generate theencryption key based on the shared secret. The generating of the sharedsecret may include one or more of a lookup, receiving the shared secret,and utilizing a Diffie Hellman approach (e.g., each DS module 111utilizes Diffie Hellman parameters to produce public values which areexchanged and utilized in a Diffie Hellman function to produce theshared secret).

The encryption key may be generated by masking the shared secret toproduce a masked shared secret and expanding the shared secret and/orthe masked shared secret. The masking includes performing adeterministic function on at least one of the shared secret and one ormore key elements. The deterministic function includes at least one of ahash algorithm (e.g., message digest (MD)-5, secure hash algorithm(SHA)-1, SHA-256, SHA 512), a hash-based message authentication code(HMAC, e.g., HMAC-MD-5), and a mask generating function (MGF). A keyelement of the one or more key elements includes at least one of asource name, a slice revision number, a requesting entity identifier(ID), and a rebuilding participants list (e.g., of the at least some ofthe DS units). The expanding includes expanding the shared secret and/orthe masked shared secret to a length substantially the same as thepartial slice 117 utilizing at least one of the MGF, a stream cipherwith hash/HMAC output (e.g., when stream ciphers uses XOR), a blockcipher (e.g., advanced encryption standard AES, data encryption standardDES) using encryption mode such as or more of output feedback (OFB),cipher feedback (CFB), and counter mode (CTR) with hash/HMAC output.

The encrypt partial slice module 115 is further operable to exclusive ORthe partial slice 117 with the encryption key of the set of encryptionkeys to produce the encrypted partial slice 119. The encrypt partialslice module 115 is further operable to assign multiple encryption keysof the set of encryption keys to the DS module 111, wherein each of themultiple encryption keys is used by another DS unit 36 of a plurality ofDS units 36. For example, a first DS unit utilizes two encryption keysthat includes encryption key 3 and encryption key 7, a second DS unitutilizes encryption key 3, and a third DS unit utilizes encryption key 7such that each encryption key is utilized an even number of times.

The encrypt partial slice module 115 is further operable to encrypt afirst partial slice of an array of partial slices (e.g., from the atleast some of the DS units of the plurality of DS units 36) using afirst encryption key of the set of encryption keys to produce a firstencrypted partial slice and exclusive OR the first encrypted partialslice and a second encrypted partial slice to produce a combinedencrypted partial slice, wherein another DS module encrypts a secondpartial slice of the array of partial slices using a second encryptionkey of the set of encryption keys to produce the second encryptedpartial slice. For example, a second DS unit produces the secondencrypted partial slice and sends the second encrypted partial slice toa first DS unit. Next, the first DS unit produces the first encryptedpartial slice, exclusive ORs the first encrypted partial slice with thesecond encrypted partial slice to produce the combined encrypted partialslice, and outputs the combined encrypted partial slice to therequesting entity 105. The requesting entity 105 is operable to receivean array of encrypted partial slices 119 from the at least some of theplurality of DS units and exclusive OR the array of encrypted partialslices to reproduce the encoded data slice.

FIG. 7B is a flowchart illustrating an example of rebuilding a slice.The method begins at step 120 where a processing module of a requestingentity issues a rebuild request regarding an encoded data slice to atleast some of a set of distributed storage (DS) units. The requestingentity includes a DS unit of the set of DS units, wherein the DS unit isto store the encoded data slice to be rebuilt. In response to therebuild request, the method continues at step 122 where a processingmodule of each of at least some of the DS units of the set of DS unitsgenerates a partial slice corresponding to the encoded data slice to berebuilt based on one of a set of encoded data slices stored by therespective DS unit to produce an array of partial slices.

The method continues at step 124 where a processing module of a DS unitencrypts the array of partial slices using a set of encryption keys,wherein each encryption key of the set of encryption keys is used 2*ntimes to produce an array of encrypted partial slices, where n is aninteger greater than or equal to 1. There is a variety of ways to do theencrypting. For example, the encrypting includes arranging, when nequals 1, at least some of DS units into DS unit pairings, wherein eachDS unit of a DS unit pairing uses a same encryption key of the set ofencryption keys. As another example, the encrypting includes, a DS unitpairing generating a shared secret and generating the same encryptionkey based on the shared secret. As yet another example, the encryptingincludes, when n equals 1 and the DS units includes an odd number of DSunits, pairing one of the DS units with two other DS units to use afirst encryption key of the set of encryption keys and arrangingremaining DS units into DS unit pairings. As a further example, theencrypting includes a DS unit exclusive ORing a partial slice of thearray of partial slices with an encryption key to produce an encryptedpartial slice.

As an even further example, the encrypting includes assigning multipleencryption keys of the set of encryption keys to a DS unit and assigningeach of the multiple encryption keys to at least one other DS unit. As astill further example, the encrypting includes encrypting, by a DS unit,a first partial slice using a first encryption to produce a firstencrypted partial slice, encrypting, by another DS unit, a secondpartial slice using a second encryption key to produce a secondencrypted partial slice, and exclusive ORing, by one or the other DSunit, the first encrypted partial slice and the second encrypted partialslice to produce a combined encrypted partial slice.

The method continues at step 126 where the processing module of therequesting entity rebuilds the encoded data slice from the array ofencrypted partial slices. The rebuilding includes exclusive ORing thearray of encryption partial slices to produce the encoded data slice.The rebuilding further includes decrypting the array of encryptedpartial slices based on the set of encryption keys to produce the arrayof partial slices and decoding the array of partial slices to rebuildthe encode data slice.

FIG. 8 is a flowchart illustrating another example of generating anencrypted partial slice. The method begins at step 132 where aprocessing module (e.g., of a dispersed storage (DS) unit) receives arebuild request from a requesting entity (e.g., another DS unit). Themethod continues at step 134 where the processing module determines keypairing requirements. The key pairing requirements includes one or moreof a performance requirement, a security requirement, and a processorloading requirement. The determination may be based on one or more ofthe rebuild request, a predetermination, a message, a dispersed storagenetwork (DSN) performance indicator, a DSN security indicator, a vaultidentifier (ID), and a requester ID. For example, the processing moduledetermines a lower than average processor loading requirement when theDSN performance indicator indicates that the DSN system is loaded morethan average. As another example, the processing module determines ahigher than average security requirement when the DSN security indicatorindicates that higher security is required.

The method continues at step 136 where the processing module determinescandidate key pairing entities. The determination may be based on one ormore of the key pairing requirements, a rebuilding topology, a securityrequirement, rebuilding participants, and a bandwidth utilizationrequirement. For example, the processing module may determine a lowerthan average number of candidate key pairing entities when the keypairing requirements includes a lower than average processor loadingrequirement. As another example, the processing module may determine ahigher than average number of candidate key pairing entities when thekey pairing requirements includes a higher than average securityrequirement.

The method continues at step 138 where the processing module selects oneor more key pairing entities of the candidate key pairing entities basedon the key pairing requirements. The selection may be based on one ormore of optimizing a match of the key pairing requirements to anestimated performance an estimated security associated with a desirednumber of candidate key pairing entities. For example, the processingmodule selects a lower than average number of key pairing entities forbetter performance and selects a higher than average number of keypairing entities for better security. As another example, the processingmodule selects a key pairing entity for utilization of an associated keyand even number of times amongst all dispersed storage (DS) units. Forinstance, the processing module selects a node ahead and a node behind areference DS unit (e.g., associated with the processing module), whereinthe node ahead, the DS unit, and the node behind are substantiallysequenced in order in accordance with a rebuilding topology. In anotherinstance, the processing module selects two nodes ahead and two nodesbehind.

The method continues at step 140 where the processing module generates ashared secret key corresponding to each of the one or more key pairingentities. The method continues at step 142 where the processing modulegenerates a partial slice. The method continues at step 144 where theprocessing module encrypts the partial slice with each of the sharedsecret keys to produce an encrypted partial slice (e.g., exclusive OR ofeach key and the partial slice). The method continues at step 146 wherethe processing module outputs the encrypted partial slice in accordancewith a rebuilding topology. For example, the processing module sends theencrypted partial slice directly to the requesting entity when therebuilding topology indicates that the requesting entity is located withthe processing module. As another example, the processing module sendsthe encrypted partial slice to the requesting entity via another DSunit, wherein the other DS unit produces a corresponding encryptedpartial slice, combines the encrypted partial slice and thecorresponding encrypted partial slice to produce a combined encryptedpartial slice (e.g., exclusive OR), and sends the combined encryptedpartial slice to the requesting entity.

FIG. 9A is a schematic block diagram of another embodiment of acomputing system that includes a management unit 18, a computing device150, and a plurality of dispersed storage (DS) units 36, which supportsa plurality of digital storage vaults. A set of the DS units 36 supportsone or more of the plurality of digital storage vaults, where a DS unit(e.g., the computing device 150) of the set stores encoded data slices(e.g., in memory 154) associated with the digital storage vault.

The computing device 150 may be implemented as at least one of a DSprocessing unit, a user device, and a DS unit 36. For example, thecomputing device 150 is implemented as a DS unit 36 of a set of DS units36 of the plurality of DS units 36. The computing device 150 includes aDS module 152 and a memory 154. The memory of 154 may be implementedutilizing one or more memory devices including one or more of a FLASHmemory, random access memory, a magnetic disk drive, and an optical diskdrive. The memory 154 may be utilized by the computing device 152 tostore software associated with the computing device 150. The softwareincludes one or more of operating system software, bootstrap firmware,application software, and software configuration information. The DSmodule 152 includes a receive update notice module 156, a determineupdate strategy module 158, and an update software module 160.

The receive update notice module 156, when operable within the computingdevice 150, causes the computing device 150 to receive a software updatenotice 162 (e.g., from the management unit 18). The software updatenotice 162 includes at least one of a software update indicator and asoftware update 166. The software update indicator includes at least oneof a software revision number and a software update retrieval location.

The determine update strategy module 158, when operable within thecomputing device 150, determines, in regards to the software updatenotice 162, an update strategy 164 for updating software of the DS unit(e.g., the computing device 150) such that at least a decode thresholdnumber of DS units 36 of the set of DS units 36 is continually availableto service access requests to the digital storage vault. The updatestrategy 164 includes at least one of never updating, updating now, andupdating later. The update strategy may be determined in a variety ofways. For example, the determine update strategy module 158 determinesthe status of the software update 166 that is used to update thesoftware and determines the update strategy 164 based on the status ofthe software update. The status of the software update includes at leastone of a time indicator, a mandatory critical status, a mandatorynoncritical status, and an optional status. As a specific example, thedetermine update strategy module 158 determines the update strategy 164to include updating now when the software update 166 includes themandatory critical status. As another specific example, the determineupdate strategy module 158 determines the update strategy 164 to includeupdating later when the software update 166 includes the mandatorynoncritical status.

As another example, the determine update strategy module 158 determinesthe update status 168 of DS units 36 in the set and determines theupdate strategy 164 based on their update status 168. The update status168 includes at least one of available, unavailable, already updated,and not already updated. As a specific example, the determine updatestrategy module 158 determines the update strategy 164 to includeupdating later when the update status 168 indicates that only a decodethreshold number of DS units 36 (e.g., including the computing device150) of the set of DS units 36 is available.

As yet another example, the determine update strategy module 158identifies a set of digital storage vaults supported by the DS unit(e.g., the computing device 150). The strategy module 158 thenidentifies other DS units that are also supporting the set of digitalstorage vaults. The strategy module then determines the update strategy164 such that at least a decode threshold number of DS units 36 for eachvault is continually available. For example, the determine updatestrategy module 158 determines the update strategy 164 to includeupdating later when the update status 168 of one set of the set of setsof DS units indicates that only a decode threshold number of DS units 36of the set of DS units 36 is available.

As a further example, the determine update strategy module 158determines priority status of at least some of the vaults anddetermining the update strategy based on the priority status of thevaults. The priority status includes at least one of high priority,general priority, low priority, and no priority. For example, the updatestrategy module 158 determines the update strategy 164 to includeupdating DS units 36 associated a first vault immediately and updatingDS units 36 associated with a second vault later when the first vault isassociated with a priority status of a greater priority than a prioritystatus of the second vault.

The update software module 160, when operable within the computingdevice 150, updates the software of the DS unit (e.g., the computingdevice 150) in accordance with the update strategy 164. For example, theupdating the software may be done by facilitating storage of thesoftware update 166 in the memory 154, facilitating replacing an olderrevision of software with the software update 166, configuring DS unitsoftware in accordance with configuration information of the softwareupdate 166, activating the software update 166, deleting the olderrevision of software, and/or deleting the older revision of softwarewhen the software update 166 is operational.

FIG. 9B is a schematic block diagram of another embodiment of acomputing system that includes a computing device 180 and a plurality ofdispersed storage (DS) units 36. The computing device 180 may beimplemented as at least one of a DS processing unit, a user device, DSunit 36, and a DS managing unit 18 of a distributed storage network(DSN). The computing device 180 includes a DS module 182. The DS module182 includes a generate notice module 184, a determine update strategymodule 186, and a facilitate software update module 188.

The generate notice module 184, when operable within a computing device180, generates and sends a software update notice 162 to the dispersedstorage (DS) units 36. The DS units 36 support digital storage vaults,where a set of the DS units 36 supports one of the digital storagevaults. The software update notice 162 includes a software updateindicator and/or a software update 166. The software update indicatorincludes a software revision number and/or a software update retrievallocation.

The determine update strategy module 186, when operable within thecomputing device 180, determines, in regards to the software updatenotice 162, an update strategy 164 for updating software of the DS units36 such that at least a decode threshold number of DS units 36 iscontinually available to service access requests to the digital storagevaults. The update strategy may be determined in a variety of ways. Forexample, the determine update strategy module 186 receives responses 190(e.g., a software revision indicator, an available indicator, and anunavailable indicator) from the DS units regarding the software updatenotice 162. The strategy module 186 then identifies a DS unit 36 inaccordance with the update strategy 164 and facilitates (e.g., send thesoftware update) updating the software of the identified DS unit. As aspecific example, the determine update strategy module sends thesoftware update 166 to the identified DS unit when the response 190 ofthe identified DS unit indicates that it has an older software versionand that it is available for updating. The strategy module may alsodetermine the update strategy in a similar manner to the strategy moduleof FIG. 9A.

The facilitate software update module 188, when operable within thecomputing device 180, facilitates updating the software of a DS unit 36in accordance with the update strategy 164. For example, the facilitatesoftware update module 188 obtains (e.g., receive, request, generate,etc.) the software update 166 and outputs it to one or more of DS units36 in accordance with the update strategy 164.

FIG. 9C is a flowchart illustrating an example of updating software. Themethod begins at step 200 where a management unit of a distributedstorage network (DSN) sends a software update notice to dispersedstorage (DS) units that support digital storage vaults. The softwareupdate notice includes a software update and/or a software updateindicator, which includes a software revision number and/or a softwareupdate retrieval location.

The method continues at step 202 where a processing module (e.g., of aDS management unit, of a DS unit) determines, in regards to the softwareupdate notice, an update strategy for updating software of the DS unitssuch that at least a decode threshold number of DS units is continuallyavailable to service access requests to the digital storage vaults.Examples of determining the update strategy have been previouslydiscussed. The method continues at step 204 where the processing moduleupdates the software of at least some of the DS units in accordance withthe update strategy.

FIG. 10A is a flowchart illustrating an example of encrypting an encodeddata slice. The method begins at step 210 where a processing module(e.g., of a dispersed storage (DS) processing unit) dispersed storageerror encodes a data segment to produce a set of encoded data slices forstorage in a dispersed storage network (DSN) memory. The methodcontinues at step 212 where the processing module obtains a secret key(e.g., retrieving it, generating it from a random key, generating itbased on a deterministic function (e.g., a hash function)).

The method continues at step 214 where the processing module encrypts anencoded data slice of the set of encoded data slices utilizing thesecret key. The method continues at step 216 where the processing moduleencrypts the secret key utilizing a public key. The processing modulethen obtains the public key from a public/private key pair associatedwith a target entity (e.g., a receiving DS unit).

The method continues at step 218 where the processing module creates apackage that includes the encrypted data slice, the encrypted secretkey, a timestamp, a sequence number, and/or an opcode (e.g., write,checked write, delete). The method continues at step 220 where theprocessing module creates a signed package (e.g., signs the packageusing a secure digital signature). For example, the processing moduleencrypts a hash digest of the package utilizing a private key associatedwith the processing module (e.g., the sender) to produce the signature.

The method continues at step 222 where the processing module sends thesigned package to a DS unit to facilitate storage of the encrypted dataslice and the encrypted secret key. The method continues at step 224where the processing module sends a certificate chain to the DS unit.For example, the processing module sends the certificate chain once perbatch of sending a plurality of signed packages to the DS unit. Asanother example, the processing module sends the certificate chain tothe DS unit with each signed package.

FIG. 10B is a flowchart illustrating an example of decrypting anencrypted data slice. The method begins at step 226 where a processingmodule (e.g., of a dispersed storage (DS) unit) receives a signedpackage and may further receive a certificate chain. The methodcontinues at step 228 where the processing module validates a signatureof the signed package. For example, the processing module decrypts thesignature utilizing a public-key associated with a sender of the signedpackage and then compares the decrypted signature to a calculated hashdigest of the package. If the comparison is favorable (e.g., thedecrypted signature is substantially the same as the calculated hashdigest), the signature is validated. Alternatively, or in addition to,the processing module validates the certificate chain when a certificatechain is received.

The method continues at step 230 where the processing module validatespermissions associated with the signed package. For example, theprocessing module compares a requester identity (ID) and an opcode to alist of allowed operations associated with the requester ID. When thesignature and permissions are valid, the method continues at step 232where the processing module decrypts an encrypted secret key utilizing aprivate key to recapture the secret key. Note that the private key maybe associated with a public/private key pair of the processing module(e.g., for a current DS unit).

The method continues at step 234 where the processing module decrypts anencrypted data slice utilizing the secret key to recapture the encodeddata slice. The method continues at step 236 where the processing modulevalidates the package. For example, the processing module verifies thata sequence number of the package compares favorably (e.g., greater than)to a previous sequence number. As another example, processing moduleverifies that a timestamp of the package compares favorably (e.g., lessthan) to at least one of a previous timestamp and a current timestamp.The method continues at step 238 where the processing module performs anoperation (e.g., write, checked write, delete) in accordance with anopcode of the package when the package is validated.

FIG. 11A is a flowchart illustrating an example of storing a datasegment, which includes similar steps to FIG. 10A. The method begins atstep 240 where a processing module (e.g., a dispersed storage (DS)processing unit) generates integrity information for a data segment tobe stored in a dispersed storage network (DSN) memory. For example, theintegrity information may be a hash digest (e.g., a hash function on thedata segment), a checksum of the data segment, and/or a signature of thedata segment (e.g., encrypting a hash of the data segment utilizing aprivate key of a public/private key pair associated with the processingmodule).

The method continues at step 242 where the processing module combines(e.g., appending, interlacing, and/or encoding the integrity informationand data segment) integrity information and the data segment to producea data package. The method continues at step 212 of FIG. 10A where theprocessing module obtains a secret key and thereafter continues at step246 where the processing module encrypts the data package utilizing thesecret key to produce an encrypted data package.

The method continues at step 248 where the processing module dispersedstorage error encodes the encrypted data package utilizing a systematicerasure code of dispersed storage error coding parameters to produce aset of encoded encrypted slices. The systematic erasure code includesmatrix multiplying a data matrix of the encrypted data package with anencoding matrix that includes a unity matrix portion to produce a matrixof encoded codes. The encoded codes are combined to produce the set ofencoded encrypted slices. The encoded codes that result from the matrixmultiplication of the elements of the data matrix with the unity matrixportion of the encoding matrix are substantially similar to thecorresponding elements of the data matrix.

The method continues at step 250 where the processing module encodes thesecret key utilizing a secret sharing algorithm (e.g., Shamir secretsharing method and/or dispersed storage error encoding) to produce a setof secret shares. Note that if the encoding includes the dispersedstorage error encoding, the encoding may utilize a different pillarwidth and/or a different decode threshold number than the dispersedstorage error encoding of the encrypted data package.

The method continues at step 252 where the processing module sends theset of encoded encrypted slices to the DSN memory for storage therein.The method continues at step 254 where the processing module sends theset of secret shares to the DSN memory for storage therein. For example,processing module sends the set of secret shares to a different portion(e.g., different DS unit) of the DSN memory as compared to where it sentthe set of encoded encrypted slices.

FIG. 11B is a flowchart illustrating an example of retrieving a datasegment. The method begins at step 256 where a processing module (e.g.,of a dispersed storage (DS) processing unit) retrieves a decodethreshold number of encoded encrypted slices of a set of encodedencrypted slices from a dispersed storage network (DSN) memory. Themethod continues at step 258 where the processing module retrieves adecode threshold number of secret shares of a set of secret shares fromthe DSN memory.

The method continues at step 260 where the processing module decodes thedecode threshold number of secret shares utilizing a secret sharingalgorithm to reproduce a secret key. The method continues at step 262where the processing module dispersed storage error decodes the decodethreshold number of encoded encrypted slices to reproduce an encrypteddata package. The method continues at step 264 where the processingmodule decrypts the encrypted data package utilizing the secret key toreproduce a data segment and recovered integrity information. Forexample, the processing module separates the decrypted data package intothe data segment and the recovered integrity information.

The method continues at step 266 where the processing module validatesthe recovered integrity information. For example, the processing modulegenerates integrity information for the data segment and compares it tothe recovered integrity information. If the comparison is favorable(e.g., substantially the same), then the integrity information isvalidated. In addition, the processing module may output the datasegment to a requesting entity when the recovered integrity informationis favorably validated.

FIG. 12A is a schematic block diagram of another embodiment of acomputing system that includes a computing device 270 and a distributedstorage network (DSN) memory 22. The distributed storage network memory22 includes a plurality of dispersed storage (DS) units 36. Thecomputing device 270 includes a DS module 272 and may be implemented asa DS processing unit, a user device, another DS unit 36, a storageintegrity processing unit, and/or a DS managing unit 18 of a DSN. Thecomputing device The DS module 272 includes an encrypt module 274, apartition module 276, a combine module 278, and an encode module 280.

The encrypt module 274, when operable within the computing device 270,encrypts a data segment 282 utilizing an encryption key to produce anencrypted data segment 284. In addition, the encrypt module 274 performsa deterministic function (e.g., a hashing function; a hash based messageauthentication code function; and/or a mask generating function) on theencrypted data segment 284 to produce a transformed representation ofthe encrypted data segment. The encrypt module 274 also masks theencryption key utilizing the transformed representation of the encrypteddata segment to produce a masked key 286. For example, the encryptmodule masks the encryption key by exclusive ORing the transformedrepresentation and the encryption key, subtracting one from the other,adding them together, adding and/or subtracting a constant to each andthen XOR, add, or subtract.

The encrypt module 274 may perform the deterministic function as acombination of deterministic functions. For example, the encrypt module274 performs the hashing function on the encrypted data segment 284 toproduce an interim value and performs the mask generating function onthe interim value to produce the transformed representation of theencrypted data segment. As another example, the encrypt module 274performs the hash based message authentication code function on theencrypted data segment 284 to produce the interim value and performs theMGF on the interim value to produce the transformed representation ofthe encrypted data segment.

The partition module 276, when operable within the computing device 270,partitions the masked key 286 into masked key partitions 288 andpartitions the encrypted data segment 284 into encrypted data segmentpartitions 290. The portioning may be done in accordance with apartitioning scheme. In this instance, the partition module 276determines the partitioning scheme based on a desired level of security,security requirements, available memory for storage, an error message,size of the data segment, size of the masked key, and/or size of theencrypted data segment. Note that the determined partitioning scheme maybe to partition the masked key and/or the encrypted data segment intoequal sized partitions, into variable sized partitions, and/or intoadaptive sized partition.

The combine module 278, when operable within the computing device 270,combines the masked key partitions 288 with the encrypted data segmentpartitions 290 to produce combined partitions 292. The combining may bedone in a variety of ways. For example, the combine module 278establishing a pseudo random combining process to combine the masked keypartitions 288 and the encrypted data segment partitions 290. As anotherexample, the combine module 278 utilizes an interleaving process tocombine the masked key partitions 288 with the f encrypted data segmentpartitions 290.

The encode module 280, when operable within the computing device 270encodes a combined partition using a dispersed storage error codingfunction to produce a set of encoded data slices 294. Alternatively, theencode module 280 may encode the combined partition by encrypting itusing a second encryption key. The encode module 280 then performs adeterministic function on the encrypted combined partition to produce arepresentation of it. The encoding module then masks the secondencryption key utilizing the transformed representation and appends thesecond masked key to the encrypted combined partition to produce afurther combined partition. The encode module then encodes the furthercombined partition using the same or a different dispersed storage errorcoding function to produce the set of encoded data slices 294.

The encode module 280 outputs the set of encoded data slices 294 forstorage in at least one DS unit 36 of a DSN memory 22. For example, theencode module generates a set of slice names corresponding to the set ofencoded data slices 294 and generates a set of write requests for theencoded data slices 294. The encode module then selects a set of storageresources (e.g., a set of DS units, DSN memory 22, a second DSN memory,and/or an adjunct memory) and outputs the write requests to the storageresources. The encode module may select the storage resources based on astorage scheme, a DSN memory availability indicator, a storage locationindicator, a user input, and/or an available adjunct memory indicator.

FIG. 12B is a flowchart illustrating an example of securing a datasegment. The method begins at step 300 where a processing module (e.g.,of a dispersed storage (DS) processing unit of a dispersed storagenetwork (DSN)) encrypts the data segment utilizing an encryption key.The method continues at step 302 where the processing module performs adeterministic function on the encrypted data segment to produce atransformed representation of the encrypted data segment. The methodcontinues at step 304 where the processing module masks the encryptionkey utilizing the transformed representation of the encrypted datasegment to produce a masked key.

The method continues at step 306 where the processing module partitionsthe masked key into masked key partitions. The method continues at step308 where the processing module partitions the encrypted data segmentinto encrypted data segment partitions. The method continues at step 310were the processing module combines the plurality of masked keypartitions with the plurality of encrypted data segment partitions toproduce a plurality of combined partitions.

The method continues at step 312 where the processing module encodes acombined partition using a dispersed storage error coding function toproduce a set of encoded data slices. The method continues at step 314where the processing module outputs the set of encoded data slices forstorage in a DS unit of the DSN. The method continues at step 316 wherethe processing module encodes remaining combined partitions using thedispersed storage error coding function to produce sets of encoded dataslices.

The method continues at step 318 where the processing module outputs thesets of encoded data slices for storage in DS units of the DSN. Forexample, the processing module outputs the encoded data slices such thata first DS unit stores a first set of the sets of encoded data slices.As another example, the processing module outputs the encoded dataslices such that a DS unit stores a first encoded data slice of the setsof encoded data slices.

FIG. 13A is a schematic block diagram of another embodiment of dispersedstorage (DS) processing module that transforms at least two encodedportions of slices (e.g., encoded portion 1 slices, encoded portion 2slices) into a data segment 340. The DS processing module includes agrid module 82, a combiner 320, a splitter 322, a hashing function 324,a de-masking function 326, and a decryptor 328. The grid module 82receives the at least two encoded portions of slices (e.g., retrievedfrom a dispersed storage network (DSN) memory) and dispersed storageerror decodes them to produce at least two portions of a secure package330. For example, the grid module 82 dispersed storage error decodesencoded portion 1 slices to produce a portion 1 of the secure packageand dispersed storage error decodes encoded portion 2 slices to producea portion 2 of the secure package. The combiner 320 combines theportions to produce the secure package 330.

The splitter 322 functions to split (e.g., de-appending,de-interleaving, and decoding) a masked key 334 and an encrypted datasegment 332 from the secure package 330. For example, the splitterde-appends the masked key 334 and the encrypted data segment 332 fromthe secure package 330 in accordance with an appending parameter.

The hashing function 324 generates a transformed data segment 336 fromthe encrypted data segment 332 utilizing a deterministic function. Thede-masking function 326 generates a key 338 from the masked key 334 andthe transformed data segment 336. For example, the de-masking function326 exclusive ORs (XOR) the masked key 334 and the transformed datasegment 336 to generate the key. As another example, the de-maskingfunction 326 XORs the transformed data segment 336 and the masked key334 to produce a modified key. The de-masking function 326 then modifies(e.g., add or subtract an offset, encrypting, XOR with a secret key,appending a secret key) the modified key to produce the key 338. Thedecryptor 328 decrypts the encrypted data segment 332 utilizing the key338 to produce the data segment 340.

In an example of operation, the grid module 82 retrieves at least adecode threshold number of slices of a set of encoded portion 1 slicesand at least a decode threshold number of slices a set of encodedportion 2 slices. Grid module 82 dispersed storage error decodes them toproduce first and second portions. The combiner 320 combines theportions to produce the secure package 330 by appending the portion 2 tothe portion 1.

The splitter 322 extracts the masked key 334 and the encrypted datasegment 332 from the secure package 330 by de-appending the masked key334 from the secure package 330. The hashing function 324 calculates amessage digest (MD)-5 hash of the encrypted data segment 332 to generatetransformed data segment 336. The de-masking function 326 calculates aXOR of the masked key 334 and the transformed data segment 336 togenerate the key 338. The decryptor 328 decrypts the encrypted datasegment 332 utilizing the key 338 to produce the data segment 340. Thedata segment 340 may subsequently be aggregated with other data segmentsto produce a data object as part of a retrieval sequence.

FIG. 13B is a flowchart illustrating another example of retrieving adata segment. The method begins with step 342 where a processing module(e.g., of a dispersed storage (DS) processing unit) facilitatesretrieving two or more sets of encoded portion slices. The methodcontinues at step 344 where the processing module dispersed storageerror decodes the two or more sets of encoded portion slices to producetwo or more portions.

The method continues at step 346 where the processing module combinesthe portions to produce a secure package in accordance with a combiningalgorithm and/or combining parameters. The method continues at step 348where the processing module splits the secure package to extract amasked key and an encrypted data segment. The method continues at step350 where the processing module transforms the encrypted data segmentutilizing a deterministic function (e.g., a hashing function) to producea transformed data segment. The method continues at step 352 where theprocessing de-masks the masked key utilizing a de-masking function toproduce a key. The method continues at step 354 where the processingmodule decrypts the encrypted data segment utilizing the key to producea data segment.

FIG. 14 is a diagram illustrating an example of a segmentationallocation table (SAT) 360 that includes a plurality of regions 1-R.Each region of the plurality of regions 1-R includes a start segmentvault source name field 362, a segment size field 364, a segmentationapproach field 366, a total length field 368, and a region hash field370. The start segment vault source name field 362 includes a vaultsource name corresponding to a first data segment of a contiguous numberof data segments that store data corresponding to a region.Alternatively, or in addition to, the start segment vault source namefield may include a file identifier (ID), a segment ID, a block ID and afile type indicator (e.g., block storage or file storage). The segmentsize field 364 includes a segment size entry indicating a number ofbytes of each segment associated with the region.

The segmentation approach field 366 includes a segmentation approachindicator, which indicates what type of segmentation is utilized whensegmenting data to produce the contiguous number of data segmentsassociated with the region. For example, segment sizes of the contiguousnumber of data segments are substantially the same when the segmentationapproach indicator indicates a flat or fixed approach. As anotherexample, segment sizes of the contiguous number of data segments startsmall and ramp up when the segmentation approach indicator indicates aramp up approach. As yet another example, segment sizes of thecontiguous number of data segments start higher and ramp down when thesegmentation approach indicator indicates a ramp down approach. In suchramping approaches, the segmentation approach field 366 may also includea starting segment size, a size increment number (e.g., the differencein size between segments), and a ramp up/down indicator.

The total length field 368 includes a length indicator (e.g., a numberof bytes) corresponding to the amount of data stored in the contiguousnumber of data segments that store data corresponding to the region.Alternatively, or in addition to, the total length field may include adata total length indicator corresponding to the amount of data storedin all regions associated with the data.

The region hash field 370 includes a deterministic function result ofapplying a deterministic function to the contiguous number of datasegments associated with the region. The deterministic function includesone or more of a hash algorithm (e.g., message digest (MD)-5, securehash algorithm (SHA)-1, SHA-256, SHA 512), a hash-based messageauthentication code (HMAC, e.g., HMAC-MD-5), and a mask generatingfunction (MGF). For example, a hash digest entry from performing a MD-5hashing function over one data segment results when the region includesone data segment. The region hash field may be utilized to determinewhether a similar data segment has already been stored in an associateddispersed storage network (DSN) memory.

The SAT 360 may be stored in a local memory associated to enable accessto a dispersed storage network (DSN) memory and/or as a SAT data segmentin the DSN memory (e.g., as a set of encoded SAT slices). A SAT vaultsource name is associated with the SAT when the SAT is stored in the DSNmemory. At least one SAT associates data to one or more regions ofcontiguous data segments, wherein each data segment of the one or morecontiguous data segments is stored as a set of encoded data slices in adispersed storage network (DSN) memory. For example, initial storage ofa file stuff.txt results in a first region stored in the DSN memory thatincludes four contiguous data segments of the initial data of stuff.txtand one data segment corresponding to the SAT. Next, an updated revisionof the file stuff.txt is stored in the DSN resulting in a second regionstored in the DSN memory that includes four more contiguous datasegments of appended data of stuff.txt and an updated SAT data segment.The SAT vault source name enables access to all of the encoded dataslices associated with the data.

FIG. 15A is a diagram illustrating an example of a slice name 372 formatthat includes a slice index field 374 and a vault source name field 376.The slice index field 374 includes a slice index entry corresponding toa slice name that may be utilized to produce a pillar numbercorresponding to a dispersed storage (DS) unit to store an associatedencoded data slice. The vault source name field 376 includes a vaultsource and entry that includes a source name field 378 and a segmentnumber field 380. The source name field 378 includes a source name entrycorresponding to the slice name. The segment number field 380 includes asegment number entry that corresponds to a segment identifier (ID) foreach segment associated with storing data and/or a segment allocationtable (SAT). For example, segment number zero is associated with a SATand segment number one or higher is associated with a first segment orsubsequent segments of a contiguous number of segment numbers associatedwith regions of data. For instance, a revision 1 SAT (e.g., of a firstrevision of a data file) is assigned a source name of AAA and a segmentnumber of 0 to produce a vault source name of AAA0 and an affiliatedrevision 1 data start (e.g., a first segment of data) is associated withthe same source name of AAA and a segment number of 1 to produce a vaultsource name of AAA1. As another instance, a revision 2 SAT (e.g., of asecond revision of the data file) is assigned a source name of BBB and asegment number of 0 to produce a vault source name of BBB0 and anaffiliated revision 2 new data start (e.g., a new second segment ascompared to revision 1) of the data is associated with the source nameof BBB and a segment number of 2 to produce a vault source name of BBB2.

The source name field 378 includes a vault ID field 382, a generationfield 384, and an object number field 386. The vault ID field 382includes a vault ID entry that associates a plurality of data as a groupof data accessible when access to such a vault is enabled (e.g., a groupof data affiliated with an entity such as a user device or a group ofuser devices) for the slice and. The generation field 384 includes ageneration entry that associates a subgroup of data associated with thevault ID entry of the slice name. For example, successive generationsmay be added over time to organize data into multiple subgroups. Theobject number field 386 (e.g., a file ID) includes an object numberentry of the slice name that identifies the data and may be createdbased on one or more of a filename, a hash of the data, a hash of thefilename, a user ID, a vault ID, and a random number. For example, anobject number of a first revision of a data file may be substantiallythe same as the object number of a second revision of the data file. Asanother example, the object number of the first revision of the datafile may be substantially different than the object number of the secondrevision of the data file.

FIG. 15B is a diagram illustrating an example of data segmentation thatincludes a segment allocation table (SAT) 388 and a plurality ofconsecutive segments 1-4 corresponding to initially storing a firstrevision of data. The SAT 388 is stored in a dispersed storage network(DSN) memory at a vault source name address of AAA0. The SAT 388includes a first region with a start segment vault source name field 362entry of AAA1, a segment size field 364 entry of 100 bytes, asegmentation approach field 366 entry of a fixed segmentation approach,a total length field 368 entry of 100 bytes, and a region hash field 370entry value of FD5396. The SAT 388 further includes a second region witha start segment vault source name of AAA2, a segment size of 100 bytes,a fixed segmentation approach, a total length of 240 bytes, and a regionhash value of 39C2DA. Each segment of the segments 1-4 of the examplecontain a maximum of 100 bytes in accordance with the segment size of100 bytes as indicated in both regions of the SAT. A segment 1 is storedin the DSN memory at a vault source name address of AAA1 in accordancewith the start segment vault source name AAA1 as indicated in region 1of the SAT. Segments 2-4 are stored in the DSN memory at vault sourcename addresses of AAA2-AAA4 in accordance with contiguous segmentnumbering as indicated in region 2 of the SAT.

FIG. 15C is a diagram illustrating another example of data segmentationthat includes a segment allocation table (SAT) 390 and a plurality ofconsecutive segments 2-5 corresponding to new segments of a secondrevision of data. The SAT 390 is stored in a dispersed storage network(DSN) memory at a vault source name address of BBB0. The SAT 390includes two regions, wherein a first region includes segments common toa first revision of the data and the second revision of the data. Thefirst region includes a start segment vault source name of AAA1, asegment size of 100 bytes, a fixed segmentation approach, a total lengthof 100 bytes, and a region hash of FD5396.

The second region includes a start segment vault source name of BBB2, asegment size of 300 bytes, a fixed segmentation approach, a total lengthof 1200 bytes, and a region hash of 9274BC. The segments 2-5 eachcontain a maximum of 300 bytes in accordance with the segment size of300 bytes as indicated in the SAT region 2. The segments 5-8 eachcontain 300 bytes in accordance with the total length of 1200 bytes asindicated in the SAT region 2. Segment 2 (e.g., a new segment 2 ascompared to a segment 2 of revision 1 of the data) is stored in adispersed storage network (DSN) memory at a vault source name address ofBBB2 in accordance with the start segment vault source name BBB2 asindicated in the SAT region 2. Segments 2-5 are stored in the DSN memoryat vault source name addresses of BBB2-BBB5 in accordance withcontiguous segment numbering and SAT region 2. Another SAT associatedwith revision 1 of the data (e.g., as discussed with reference to FIG.15B) and old segments 2-4 may be deleted when the SAT associated withrevision 2 of the data is stored when revision one of the data is nolonger required.

FIG. 16A is a schematic block diagram of another embodiment of acomputing system that includes a computing device 400 and a dispersedstorage network (DSN) memory 22 of a DSN. The distributed storagenetwork memory 22 includes a plurality of dispersed storage (DS) units36. The computing device 400 includes a DS module 402 and may beimplemented as a DS processing unit, a user device, a storage integrityprocessing unit, and/or a DS managing unit 18 of a DSN. The DS module402 includes a generate preliminary storage information module 404, anaccess storage information module 406, a compare information module 408,a generate storage information module 410, and a store new data module412.

The generate preliminary storage information module 404, when operablewithin the computing device 400 generates preliminary DSN storageinformation 416 for data 414 to be stored in a DSN (e.g., in the DSNmemory 22). The preliminary DSN storage information 416 includes, forone or more portions (e.g., regions) of the data 414, one or more ofdeterministic function representations of the data 414, a total lengthindicator, a segmentation approach, a segment size, and one or moreregion indicators. For example, the generate preliminary storageinformation module 404 may generate the preliminary DSN storageinformation by accessing a lookup using a data identifier (ID)associated with the data 414. As a specific example, the generatepreliminary storage information module 404 receives the data ID,associates the data ID with a vault ID, accesses a registry based on thevault ID, and retrieves the segmentation approach and the segment size.As another example, the generate preliminary storage information module404 may generate the preliminary DSN storage information by receivingthe data 414 and analyzing it and/or performing a deterministic functionon the data 414.

The generate preliminary storage information module 404 also segmentsthe data 414 into segments in accordance with the preliminary DSNstorage information. For example, the generate preliminary storageinformation module 404 segments the data 414 into a first subset ofsegments corresponding to a first region and into a second subset ofsegments corresponding to a second region. The generate preliminarystorage information module 404 then performs a deterministic function onsegments of the first and second regions to produce a deterministicrepresentation of the first and second regions.

The access storage information module 406, when operable within thecomputing device 400, accesses DSN storage information 418 regardingother data stored in the DSN. For example, the access storageinformation module 406 accesses one or more segment allocation tablesfor the other data. Note that the DSN storage information 418 includes,for one or more portions (e.g., regions) of the other data, one or moreof deterministic function representations of the other data, a totallength indicator of the other data, a segmentation approach of the otherdata, a segment size of the other data, and one or more regionindicators of the other data.

As another example, the access storage information module 406 identifiesa relationship between the data 414 and the other data and accessing theDSN storage information 418 of the other data based on the relationship.Note that the relationship includes a same data ID, a same requestingentity ID, a same user ID, a same vault ID, and/or a same group ofusers.

The compare information module 408, when operable within the computingdevice 400, compares the preliminary DSN storage information 416 for thedata 414 with the DSN storage information 418 regarding the other data.For example, the compare information module 408 generates deterministicfunction representations of the data 414 and compares it with thedeterministic function representations of the other data. When thecomparison is favorable (e.g., substantially similar), the compareinformation module 414 indicates that the preliminary DSN storageinformation 416 is comparable to the DSN storage information 418 of theother data.

The generate storage information module 410, when operable within thecomputing device 400, generates DSN storage information for remainingportions of the data 420 when the comparison result was favorable. Themodule 410 also generates DSN storage information 422 for the data 414based on the DSN storage information of the other data and the remainingportions DSN storage information. For example, the generate storageinformation module 410 generates the DSN storage information 420 for thedata by associating at least the portion of the data with the DSNstorage information of at least the portion of the other data. As aspecific example, the generate storage information module 410 utilizes asegment allocation table of the DSN storage information of at least theportion of the other data as a segment allocation table for at least aportion of the data.

As another example, the generate storage information module 410generates the DSN storage information 420 for the data by creating asegment allocation table that includes data portioning information forthe portions of the data and deterministic function representations ofthe portions of the data, wherein the portions of the data include theat least the portion of the data and the remaining portions of the data420. As a specific example, the generate storage information module 410generates a new region entry of DSN storage information for theremaining portions of the data 420, wherein the new region entry isincluded in the segment allocation table.

The store new data module 412, when operable within the computing device400, dispersed storage error encodes the remaining portions of the data420 to produce dispersed storage error encoded data 424. The store newdata module 412 also outputs the DS encoded data 424 for storage in theDSN memory 22 in accordance with the remaining portions DSN storageinformation. For example, the store new data module 412 segments theremaining portions of the data 420 in accordance with the remainingportions DSN storage information (e.g., segment size, segmentationapproach) to produce a plurality of segments, encodes each segment ofthe rally of segments utilizing a dispersed storage error codingfunction to produce a plurality of sets of encoded data slices, and foreach plurality of sets of encoded data slices, outputting the pluralityof sets of encoded data slices to the DSN memory 22 for storage therein.

FIG. 16B is a flowchart illustrating an example of storing segmenteddata. The method begins at step 430 where a processing module (e.g., ofa dispersed storage (DS) processing unit of a dispersed storage network(DSN)) generates preliminary dispersed storage network (DSN) storageinformation for data to be stored in a DSN. The method continues at step432 where the processing module accesses DSN storage informationregarding other data stored in the DSN. The accessing DSN storageinformation of the other data includes accessing one or more segmentallocation tables for the other data, wherein a segment allocation tableof the one or more segment allocation tables includes data portioninginformation for portions of the other data and deterministic functionrepresentations of the portions of the other data. The accessing DSNstorage information of the other data further includes identifying arelationship between the data and the other data and accessing the DSNstorage information of the other data based on the relationship.

The method continues at step 434 where the processing module comparesthe preliminary DSN storage information for the data with the DSNstorage information regarding the other data. The comparing furtherincludes generating deterministic function representations of the dataand comparing the deterministic function representations of the datawith the deterministic function representations of the portions of theother data. The comparing further includes segmenting the data into aplurality of segments in accordance with at least one of the pulmonaryDSN storage information and the DSN storage information regarding theother data. For example, the processing module compares a hash digest ofa first region of the data (e.g., a message digest 5 hash over 25 datasegments of the region) to a first region hash digest associated withthe other data (e.g., from a segment allocation table retrieved from theDSN).

When at least a portion of the data has compatible preliminary DSNstorage information with DSN storage information of at least a portionof the other data, the method continues at step 436 where the processingmodule generates DSN storage information for remaining portions of thedata to produce remaining portions DSN storage information, wherein theat least the portion of the data includes one or more of the pluralityof segments. The method continues at step 438 where the processingmodule generates DSN storage information for the data based on the DSNstorage information of the at least the portion of the other data andthe remaining portions DSN storage information.

The generating the DSN storage information for the data further includesassociating the at least the portion of the data with the DSN storageinformation of the at least the portion of the other data. Thegenerating the DSN storage information for the data further includescreating a segment allocation table that includes data portioninginformation for the portions of the data and deterministic functionrepresentations of the portions of the data, wherein the portions of thedata include the at least the portion of the data and the remainingportions of the data. For example, the processing module creates a newregion entry including a start segment vault source name, a segmentsize, a segmentation approach, a total length of the remaining portionsof data, and a region hash digest over one or data segments of theregion as the deterministic function representation. The methodcontinues at step 440 where the processing module dispersed storageerror encodes the remaining portions of the data to produce dispersedstorage error encoded data. The method continues at step 442 where theprocessing module stores the dispersed storage error encoded data inaccordance with the remaining portions DSN storage information.

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “operably coupled to”, “coupled to”, and/or “coupling” includesdirect coupling between items and/or indirect coupling between items viaan intervening item (e.g., an item includes, but is not limited to, acomponent, an element, a circuit, and/or a module) where, for indirectcoupling, the intervening item does not modify the information of asignal but may adjust its current level, voltage level, and/or powerlevel. As may further be used herein, inferred coupling (i.e., where oneelement is coupled to another element by inference) includes direct andindirect coupling between two items in the same manner as “coupled to”.As may even further be used herein, the term “operable to” or “operablycoupled to” indicates that an item includes one or more of powerconnections, input(s), output(s), etc., to perform, when activated, oneor more its corresponding functions and may further include inferredcoupling to one or more other items. As may still further be usedherein, the term “associated with”, includes direct and/or indirectcoupling of separate items and/or one item being embedded within anotheritem. As may be used herein, the term “compares favorably”, indicatesthat a comparison between two or more items, signals, etc., provides adesired relationship. For example, when the desired relationship is thatsignal 1 has a greater magnitude than signal 2, a favorable comparisonmay be achieved when the magnitude of signal 1 is greater than that ofsignal 2 or when the magnitude of signal 2 is less than that of signal1.

As may also be used herein, the terms “processing module”, “processingcircuit”, and/or “processing unit” may be a single processing device ora plurality of processing devices. Such a processing device may be amicroprocessor, micro-controller, digital signal processor,microcomputer, central processing unit, field programmable gate array,programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on hard coding of the circuitry and/oroperational instructions. The processing module, module, processingcircuit, and/or processing unit may be, or further include, memoryand/or an integrated memory element, which may be a single memorydevice, a plurality of memory devices, and/or embedded circuitry ofanother processing module, module, processing circuit, and/or processingunit. Such a memory device may be a read-only memory, random accessmemory, volatile memory, non-volatile memory, static memory, dynamicmemory, flash memory, cache memory, and/or any device that storesdigital information. Note that if the processing module, module,processing circuit, and/or processing unit includes more than oneprocessing device, the processing devices may be centrally located(e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that if the processing module, module, processing circuit,and/or processing unit implements one or more of its functions via astate machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory and/or memory element storing the correspondingoperational instructions may be embedded within, or external to, thecircuitry comprising the state machine, analog circuitry, digitalcircuitry, and/or logic circuitry. Still further note that, the memoryelement may store, and the processing module, module, processingcircuit, and/or processing unit executes, hard coded and/or operationalinstructions corresponding to at least some of the steps and/orfunctions illustrated in one or more of the Figures. Such a memorydevice or memory element can be included in an article of manufacture.

The present invention has been described above with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claimed invention. Further, theboundaries of these functional building blocks have been arbitrarilydefined for convenience of description. Alternate boundaries could bedefined as long as the certain significant functions are appropriatelyperformed. Similarly, flow diagram blocks may also have been arbitrarilydefined herein to illustrate certain significant functionality. To theextent used, the flow diagram block boundaries and sequence could havebeen defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claimed invention. One of average skill in the artwill also recognize that the functional building blocks, and otherillustrative blocks, modules and components herein, can be implementedas illustrated or by discrete components, application specificintegrated circuits, processors executing appropriate software and thelike or any combination thereof.

The present invention may have also been described, at least in part, interms of one or more embodiments. An embodiment of the present inventionis used herein to illustrate the present invention, an aspect thereof, afeature thereof, a concept thereof, and/or an example thereof. Aphysical embodiment of an apparatus, an article of manufacture, amachine, and/or of a process that embodies the present invention mayinclude one or more of the aspects, features, concepts, examples, etc.described with reference to one or more of the embodiments discussedherein. Further, from figure to figure, the embodiments may incorporatethe same or similarly named functions, steps, modules, etc. that may usethe same or different reference numbers and, as such, the functions,steps, modules, etc. may be the same or similar functions, steps,modules, etc. or different ones.

Unless specifically stated to the contra, signals to, from, and/orbetween elements in a figure of any of the figures presented herein maybe analog or digital, continuous time or discrete time, and single-endedor differential. For instance, if a signal path is shown as asingle-ended path, it also represents a differential signal path.Similarly, if a signal path is shown as a differential path, it alsorepresents a single-ended signal path. While one or more particulararchitectures are described herein, other architectures can likewise beimplemented that use one or more data buses not expressly shown, directconnectivity between elements, and/or indirect coupling between otherelements as recognized by one of average skill in the art.

The term “module” is used in the description of the various embodimentsof the present invention. A module includes a processing module, afunctional block, hardware, and/or software stored on memory forperforming one or more functions as may be described herein. Note that,if the module is implemented via hardware, the hardware may operateindependently and/or in conjunction software and/or firmware. As usedherein, a module may contain one or more sub-modules, each of which maybe one or more modules.

While particular combinations of various functions and features of thepresent invention have been expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent invention is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

What is claimed is:
 1. A method for execution by a computer, the methodcomprises: retrieving a plurality of sets of encoded data slices,wherein a set of encoded data slices corresponds to a dispersed storageerror encoded combined partition of a plurality of combined partitions;dispersed storage error decoding the plurality of sets of encoded dataslices to reproduce the plurality of combined partitions; separating theplurality of combined partitions into a plurality of masked keypartitions and a plurality of encrypted data segment partitions;combining the plurality of masked key partitions to produce a maskedkey; combining the plurality of encrypted data segment partitions toproduce an encrypted data segment; performing a deterministic functionon the encrypted data segment to produce a transformed representation ofthe encrypted data segment; unmasking the masked key utilizing thetransformed representation of the encrypted data segment to recover anencryption key; and decrypting the encrypted data segment using theencryption key to recover a data segment.
 2. The method of claim 1further comprises: determining a partitioning scheme based on a desiredlevel of security; and separating the plurality of combined partitionsin accordance with the partitioning scheme.
 3. The method of claim 1,wherein the separating the plurality of masked key partitions from theplurality of encrypted data segment partitions comprises: determining apseudo random combining process that was used to combine the pluralityof masked key partitions and the plurality of encrypted data segmentpartitions; and separating the plurality of masked key partitions fromthe plurality of encrypted data segment partitions in accordance withthe pseudo random combining process.
 4. The method of claim 1, whereinthe separating the plurality of masked key partitions from the pluralityof encrypted data segment partitions further comprises: separating theplurality of masked key partitions with the plurality of encrypted datasegment partitions in accordance with an interleaving process.
 5. Themethod of claim 1 further comprises: for a set of encoded data slices ofthe plurality of sets of encoded data slices: dispersed storage errordecoding the set of encoded data slices to produce a further combinedpartition; separating a second masked key and an encrypted combinedportion from the further combined partition; performing a deterministicfunction on the encrypted combined partition to produce a transformedrepresentation of the encrypted combined partition; unmasking the secondmasked key utilizing the transformed representation of the encryptedcombined partition to produce a second encryption key; and decryptingthe encrypted combined partition utilizing the second encryption key toproduce a combined partition of the plurality of combined portions.
 6. Acomputer readable storage device comprises: a first memory section thatstores operational instructions that, when executed by a computingdevice, causes the computing device to: retrieve a plurality of sets ofencoded data slices, wherein a set of encoded data slices corresponds toa dispersed storage error encoded combined partition of a plurality ofcombined partitions; a second memory section that stores operationalinstructions that, when executed by the computing device, causes thecomputing device to: dispersed storage error decode the plurality ofsets of encoded data slices to reproduce the plurality of combinedpartitions; a third memory section that stores operational instructionsthat, when executed by the computing device, causes the computing deviceto: separate the plurality of combined partitions into a plurality ofmasked key partitions and a plurality of encrypted data segmentpartitions; combine the plurality of masked key partitions to produce amasked key; combine the plurality of encrypted data segment partitionsto produce an encrypted data segment; perform a deterministic functionon the encrypted data segment to produce a transformed representation ofthe encrypted data segment; unmask the masked key utilizing thetransformed representation of the encrypted data segment to recover anencryption key; and a fourth memory section that stores operationalinstructions that, when executed by the computing device, causes thecomputing device to: decrypt the encrypted data segment using theencryption key to recover a data segment.
 7. The computer readablestorage device of claim 6, wherein the third memory section furtherstores operational instructions that, when executed by the computingdevice, causes the computing device to: determine a partitioning schemebased on a desired level of security; and separate the plurality ofcombined partitions in accordance with the partitioning scheme.
 8. Thecomputer readable storage device of claim 6, wherein the third memorysection further stores operational instructions that, when executed bythe computing device, causes the computing device to separate theplurality of masked key partitions from the plurality of encrypted datasegment partitions by: determining a pseudo random combining processthat was used to combine the plurality of masked key partitions and theplurality of encrypted data segment partitions; and separating theplurality of masked key partitions from the plurality of encrypted datasegment partitions in accordance with the pseudo random combiningprocess.
 9. The computer readable storage device of claim 6, wherein thethird memory section further stores operational instructions that, whenexecuted by the computing device, causes the computing device toseparate the plurality of masked key partitions from the plurality ofencrypted data segment partitions by: separating the plurality of maskedkey partitions with the plurality of encrypted data segment partitionsin accordance with an interleaving process.
 10. The computer readablestorage device of claim 6, wherein the first memory section furtherstores operational instructions that, when executed by the computingdevice, causes the computing device to: for a set of encoded data slicesof the plurality of sets of encoded data slices: dispersed storage errordecode the set of encoded data slices to produce a further combinedpartition; separate a second masked key and an encrypted combinedportion from the further combined partition; perform a deterministicfunction on the encrypted combined partition to produce a transformedrepresentation of the encrypted combined partition; unmask the secondmasked key utilizing the transformed representation of the encryptedcombined partition to produce a second encryption key; and decrypt theencrypted combined partition utilizing the second encryption key toproduce a combined partition of the plurality of combined portions. 11.A computer comprises: an interface; memory; and a processing moduleoperably coupled to the interface and to the processing module, whereinthe processing module is operable to: retrieve a plurality of sets ofencoded data slices, wherein a set of encoded data slices corresponds toa dispersed storage error encoded combined partition of a plurality ofcombined partitions; dispersed storage error decode the plurality ofsets of encoded data slices to reproduce the plurality of combinedpartitions; separate the plurality of combined partitions into aplurality of masked key partitions and a plurality of encrypted datasegment partitions; combine the plurality of masked key partitions toproduce a masked key; combine the plurality of encrypted data segmentpartitions to produce an encrypted data segment; perform a deterministicfunction on the encrypted data segment to produce a transformedrepresentation of the encrypted data segment; unmask the masked keyutilizing the transformed representation of the encrypted data segmentto recover an encryption key; and decrypt the encrypted data segmentusing the encryption key to recover a data segment.
 12. The computer ofclaim 11, wherein the processing module is further operable to:determine a partitioning scheme based on a desired level of security;and separate the plurality of combined partitions in accordance with thepartitioning scheme.
 13. The computer of claim 11, wherein theprocessing module is further operable to separate the plurality ofmasked key partitions from the plurality of encrypted data segmentpartitions by: determining a pseudo random combining process that wasused to combine the plurality of masked key partitions and the pluralityof encrypted data segment partitions; and separating the plurality ofmasked key partitions from the plurality of encrypted data segmentpartitions in accordance with the pseudo random combining process. 14.The computer of claim 11, wherein the processing module is furtheroperable to separate the plurality of masked key partitions from theplurality of encrypted data segment partitions by: separating theplurality of masked key partitions with the plurality of encrypted datasegment partitions in accordance with an interleaving process.
 15. Thecomputer of claim 11, wherein the processing module is further operableto: for a set of encoded data slices of the plurality of sets of encodeddata slices: dispersed storage error decode the set of encoded dataslices to produce a further combined partition; separate a second maskedkey and an encrypted combined portion from the further combinedpartition; perform a deterministic function on the encrypted combinedpartition to produce a transformed representation of the encryptedcombined partition; unmask the second masked key utilizing thetransformed representation of the encrypted combined partition toproduce a second encryption key; and decrypt the encrypted combinedpartition utilizing the second encryption key to produce a combinedpartition of the plurality of combined portions.